Hi What is the per leg voltage of an 3phase generator?
It is a old delco 20kw 60 amp per leg unit.
three wire setup
Want to know if you use two legs to make a standard 120/240 volt panel box and one 120 volt box you would have a system that puts out 120 amps between the two septate panel boxes?
You can not get 120/240V from a 3-phase system. The output will be 120/208V. If the alternator uses a six wire system it may be rewired to supply 120/240V but the power capacity will reduce to 2/3 original or about 13kW.
I have a quick hand drawing showing how the lines are reconfigured to supply single phase 120/240V. Clearly not intended as wiring instructions, but should give an idea what happens.
http://members.rennlist.org/warren/3-phase.jpg
There is something not quite right with your question. If your generator uses a total of three wires at the output you are either missing the neutral from a 3-phase system, or it is actually a single phase system already. Please double check the information you have supplied and a better response can be given.
Flyye Molle Triangular Drop Leg Panel (Airsoft-Club.com)